1. Field of the Invention
The present invention relates generally to a receiver, and particularly to a receiver provided with a circuit in which the change-over between transmitting and receiving states of an opposite station can be easily recognized.
2. Description of the Prior Art
In the case of performing intercommunication by a transmitter and receiver combination, when the transmitting state is changed-over to the receiving state, it is necessary to say, for example, "Go-ahead, please" for maintenance of good timing in the transition of the transmitting and receiving states between a principal station and its opposite station. However, it is troublesome to say Go-ahead, please every time the transmitting state is changed-over to the receiving state. Likewise, when an opposite station is calling a principal station, it is inconvenient to say, for example, "We are on the air, do you hear us?"
Accordingly, it would be desirable when the transmitting state is switched to the receiving state, that a specific change-over sound would be automatically transmitted thereby to inform the principal station that the opposite station has been changed-over from the transmitting state to the receiving state. However, the transmission of such a specific oscillating sound may be legally prohibited in a field of simple radio service, so that any means for instructing the change-over has not been provided in the prior art transmitter and receiver. Hence, an arrangement which produces a change-over sound dependent upon the presence of a signal carrier without the transmission of a change-over signal at the beginning or end of transmission would be highly useful.